EP0514344B1 - Tubular, gapless printing blanket - Google Patents

Description

The invention relates to blankets for blanket cylinders in web offset printing presses and in particular to a gap-free, sleeve-shaped blanket.

Wherever in the present technical documents (including the claims), for the sake of simplicity, the expression "rubber blanket" be it as an independent word or be used in word compositions, this generally means a "printing blanket made of an elastic material".

A web offset printing press typically comprises a plate cylinder, a blanket cylinder and a printing cylinder, which are rotatably mounted in the printing press. The plate cylinder carries a printing plate with a hard surface, which determines the image to be printed. The blanket cylinder carries a blanket with an elastic surface, which comes into contact with the printing plate in the nip between the plate cylinder and the blanket cylinder. A web to be printed moves through the nip between the blanket cylinder and the impression cylinder. Color is applied to the printing plate on the plate cylinder. A colored print image is picked up by the blanket in the nip between the blanket cylinder and the plate cylinder and transferred to the web. The impression cylinder can be another blanket cylinder for printing on the opposite side of the web.

A conventional rubber blanket is made as a flat plate. Such a blanket is supported on a blanket cylinder by wrapping the plate around the blanket cylinder and securing the respective ends of the plate in an axially extending gap in the blanket cylinder. The adjacent respective ends of the plate define a gap which extends axially along the length of the rubber blanket. The blanket gap moves through the nip between each revolution of the blanket cylinder Blanket cylinder and the plate cylinder and also through the nip between the blanket cylinder and the impression cylinder.

If the front and rear edge of the rubber blanket, which determines the gap, move through the roller gap between the rubber blanket cylinder and an adjacent cylinder, the rubber blanket cylinder and the adjacent cylinder are each relieved or relieved of pressure. This repeated pressure relief or stress on the blanket gap causes vibrations and shock loads on the cylinders throughout the press. Such vibrations and shock loads adversely affect print quality. For example, at the time the nip in the blanket triggers pressure relief and stress in the nip between the blanket cylinder and the plate cylinder, printing takes place on the web moving through the nip between the blanket cylinder and the impression cylinder. Any movement of the blanket cylinder or blanket caused by pressure relief and loading at this time can smear the print image transferred from the blanket to the web. Similarly, when the gap in the blanket moves through the nip between the blanket cylinder and the impression cylinder, a print image picked up by the blanket in the other nip from the printing plate may be smeared. The consequence of the vibrations and shock loads caused by the gap in the blanket was an undesirably low limit on the speed at which printing presses can be operated with print quality which is still acceptable.

Another problem that arises from the gap between the adjacent ends of a conventional blanket is the circumferential emptiness determined by the width of the gap. This from the width of the gap certain emptiness interrupts and reduces the circumferential length of the printing surface on the blanket cylinder. As a result, an area of the web remains unprinted with each revolution of the blanket cylinder. These unprinted areas of the web reduce productivity and increase waste. In addition, it is not easy to correctly install such a conventional blanket on a blanket cylinder. This can result in significant downtime, which can be expensive. In addition, the blanket cylinder itself must be equipped with means for attaching the respective ends of the blanket to keep it in place.

Another problem associated with conventional blankets arises from the pressure exerted on the elastic surface of the blanket by the rigid surface of the printing plate in the nip between the blanket cylinder and the plate cylinder. The elastic surface of the rubber blanket is pressed in by the roller gap from the rigid surface of the printing plate as it moves. In the middle of the nip, the cylindrical contour of the rigid pressure plate presses a similar cylindrical recess into the elastic rubber blanket. These depressions pressed into the elastic rubber blanket threaten to produce beads at the respective ends of the recess, which appear on the two circumferential sides of the nip as standing waves on the surface of the rubber blanket. As the rubber blanket moves in and out of the nip, a point on its surface moves upward and over such standing waves. For comparison with a point on the rigid cylindrical surface of the printing plate, a point on the elastic surface of the rubber blanket is directed sideways for a greater distance as it moves through the nip. This means that these surfaces at the nip have different speeds. A difference in the surface speed can slip between the Surfaces cause what can smear the ink transferred from one surface to the other.

US 4,812,357 discloses a rubber blanket which is constructed from a plurality of layers lying one above the other. A base layer consists of at least two woven textile layers, which are connected to one another by means of an adhesive layer. An elastic layer is applied to this base layer, on which in turn an elastomer-reinforced layer is attached. Finally, the elastomer-reinforced layer carries the color-guiding surface with which a print image can be printed on a material web.

As is known, rubber blankets contain compressible, rubber-like polymers which can be compressed under the pressure exerted by the printing plate in the nip. Pressing the blanket together in the nip reduces the tendency for beads to form on both sides of the nip. Standing waves that could smear the printing ink on the rotating rubber blanket are thus reduced; however, repeated compression and expansion of the compressible rubbery polymer can cause the blanket to overheat.

EP-A-0 421 145 relates to a lithographic printing machine. A tubular rubber blanket, which is removably attached to a blanket cylinder and has a coherent, gap-free outer surface, is in rolling contact with a pressure plate on a plate cylinder. The blanket consists at least partially of a compressible material which is pressed together by the plate cylinder at a pressure gap between the plate cylinder and the blanket cylinder. The outer surface of the rubber blanket has a peripheral speed that is immediate at points in front of the printing nip, at the printing nip and immediately behind the printing nip, in order to prevent smearing of the printed image at the printing nip. The rubber blanket can comprise an outer layer made of non-compressible material and an inner layer made of compressible material. The outer layer of the rubber blanket is deformable in order to compress the inner layer of the rubber blanket. The inner layer contains a large number of bubbles which are relatively large before the outer layer of the rubber blanket is deformed by a pressure plate on the plate cylinder and which are relatively small in a partial area of the inner layer of the rubber blanket which is then compressed by deformation of the outer layer of the rubber blanket. The blanket has an inner metal bushing which is tensioned by the blanket cylinder, thereby holding the blanket on the blanket cylinder.

EP-A-0 452 184 (prior art according to Art. 54 (3) EPC) discloses a multi-layer rubber blanket sleeve with a rubber layer containing cells adhering to the cylinder, on which a layer of hard elastomer and then a pressure layer are applied.

The present invention provides a sleeve-shaped blanket which enables a printing machine to run at high speeds without excessive vibration or shock, without slippage of the printing surfaces - which could smear the ink - and without overheating.

According to the invention the object is solved by the features of claim 1.

The sleeve-shaped rubber blanket further comprises a seamless, sleeve-shaped printing layer with a continuous, gap-free cylindrical printing surface.

The sleeve-shaped rubber blanket according to the invention advantageously has a seamless and gap-free sleeve-like shape through its various layers, including a continuous, gap-free cylindrical printing surface. When the sleeve-shaped blanket moves through the nip between a blanket cylinder and a plate cylinder, its profile at the nip remains unchanged. The pressure ratio between the sleeve-shaped rubber blanket and the printing plate thus remains constant during the operation of the printing press, and the movement of the sleeve-shaped rubber blanket through the nip does not cause vibrations or shock loads. There is also less waste and increased productivity because there is no gap on the surface of the sleeve-shaped rubber blanket.

Furthermore, the inextensible layer of the sleeve-shaped rubber blanket prevents standing waves from forming on the outer printing surface, which could smear the inked printed image.

In the preferred embodiments of the present invention, the cavities in the compressible layer of the tubular rubber blanket are micropores. The micropores are formed by compressible microspheres, which are evenly distributed in the first sleeve-shaped body made of elastic polymer. The compressible layer preferably comprises a compressible tissue together with compressible microspheres. The compressible fabric is contained as a spiral thread through the compressible layer and around the underlying cylindrical sleeve. The thread heats up less than the surrounding elastic polymer when the tubular rubber blanket is actuated, so that the tubular rubber blanket remains cooler during operation.

In a preferred method of manufacturing the tubular rubber blanket, the compressible layer is coated by coating a compressible thread a mixture of rubber putty and microspheres and formed by spirally winding the coated thread around the cylindrical sleeve. The non-stretchable layer is similarly formed by coating a non-stretchable thread with a rubber cement that does not contain micropores and spirally winding the coated thread around the compressible layer underneath. The inextensible thread thus forms a circumferentially inextensible sleeve-shaped lower layer, and gives the inextensible layer the inextensibility. The pressure layer is formed over the inextensible layer by wrapping an unvulcanized elastomer over the inextensible layer and securing it with adhesive tape. The bonded structure is vulcanized so that the overlying layers of elastic polymer take on an endless, seamless, sleeve-like shape.

Fig. 1

ist eine schematische Darstellung eines Druckwerks mit dem erfindungsgemäßen hülsenförmigen Gummituch;

Fig. 2

ist eine schematische, Darstellung des in Fig. 1 gezeigten Gummituchs;

Fig. 3

ist eine Teilansicht der Linie 3-3 der Fig. 2;

Fig. 4

ist eine vergrößerte Teilansicht eines Teils des in Fig. 1 gezeigten Druckwerks;

Fig. 5

ist eine Darstellung des Standes der Technik;

Fig. 6

ist eine schematische Darstellung eines Herstellungsverfahrens des erfindungsgemäßen hülsenförmigen Gummituchs;

Fig. 7

ist Teil einer Teilansicht des hülsenförmigen Gummituchs gemäß einer alternativen Ausführungsform der Erfindung;

Fig. 8A bis 8C

sind schematische Darstellungen von Herstellungsverfahren des hülsenförmigen Gummituchs der Fig. 7;

Fig. 9A und 9B

sind schematische Darstellungen eines Teils eines hülsenförmigen Gummituchs gemäß einer weiteren alternativen Ausführungsform der Erfindung;

Fig. 10

ist eine schematische Darstellung eines Teils des hülsenförmigen Gummituchs gemäß einer weiteren alternativen Ausführungsform der Erfindung;

Fig. 11A und 11B

sind schematische Darstellungen eines Teils des hülsenförmigen Gummituchs gemäß einer weiteren alternativen Ausführungsform der Erfindung;

Fig. 12

ist Teil einer Teilansicht des hülsenförmigen Gummituchs gemäß einer zusätzlichen Ausführungsform der Erfindung; und

Fig. 13

ist Teil einer Teilansicht gemäß einer weiteren alternativen Ausführungsform der Erfindung.

An embodiment of the invention is explained in more detail with reference to the accompanying drawings described below:

Fig. 1

is a schematic representation of a printing unit with the sleeve-shaped rubber blanket according to the invention;

Fig. 2

Figure 3 is a schematic illustration of the blanket shown in Figure 1;

Fig. 3

Figure 3 is a partial view of line 3-3 of Figure 2;

Fig. 4

is an enlarged partial view of part of the printing unit shown in Fig. 1;

Fig. 5

Figure 3 is a prior art illustration;

Fig. 6

is a schematic representation of a manufacturing process of the invention sleeve-shaped rubber blanket;

Fig. 7

is part of a partial view of the sleeve-shaped rubber blanket according to an alternative embodiment of the invention;

8A to 8C

are schematic representations of manufacturing processes of the sleeve-shaped rubber blanket of Fig. 7;

Figures 9A and 9B

are schematic representations of part of a sleeve-shaped rubber blanket according to a further alternative embodiment of the invention;

Fig. 10

is a schematic representation of a portion of the sleeve-shaped rubber blanket according to another alternative embodiment of the invention;

11A and 11B

are schematic representations of a portion of the sleeve-shaped rubber blanket according to a further alternative embodiment of the invention;

Fig. 12

is part of a partial view of the sleeve-shaped rubber blanket according to an additional embodiment of the invention; and

Fig. 13

is part of a partial view according to a further alternative embodiment of the invention.

In Fig. 1, a printing unit 10 is shown, which has a blanket cylinder with a sleeve-shaped blanket 14, which was produced according to the present invention. The printing unit 10 is, for example, an offset printing machine with a multiplicity of rollers for transferring printing ink from an ink fountain 16 to a printing plate 18 located on a plate cylinder 20.

The sleeve-shaped blanket 14 on the blanket cylinder 12 transfers the colored printing image from the printing plate 18 to a continuous web 21.

An ink fountain roller 22 receives ink from the ink fountain 16. A lift roller 24 reciprocates between the ink fountain roller 22 and a first rub roller 26 to transfer ink from the ink fountain roller 22 to the first rub roller 26, as shown in FIG. 1. A plurality of successive rubbing rollers 26 transfer ink from the first rubbing roller 26 to a group of inking rollers 28, which in turn transfer the ink to the printing plate 18 located on the plate cylinder 20. A second blanket cylinder 30 with a second sleeve-shaped blanket 32 is only partially shown in FIG. 1 as an illustration of a second printing unit for simultaneous printing on the opposite side of the web 21. The blanket cylinders 12 and 30 serve as printing cylinders for one another. The rollers and cylinders are connected to one another by gears and are driven by drive devices in a known manner. The lifting roller 24 is moved in a known manner by a reciprocating mechanism 36.

The sleeve-shaped rubber blanket 14 has an endless, gap-free cylindrical inner surface 40 which is in close frictional contact with the cylindrical outer surface 42 of the rubber blanket cylinder 12. The blanket cylinder 12 has an inner lumen 44 and a plurality of passages 46 which extend radially from the inner lumen 44 to the cylindrical outer surface 42. A source 50 of pressurized gas communicates with the inner lumen 44 in the blanket cylinder 12 and generates a stream of pressurized gas which is directed from the inner lumen 44 and the radially extending passages 46 onto the cylindrical inner surface 40 of the sleeve-shaped blanket 14 is.

When a stream of pressurized gas hits the cylindrical inner surface 40 of the sleeve-shaped rubber blanket 14, it deforms a little elastically, so that its diameter increases. The sleeve-shaped rubber blanket 14 can then easily be pushed onto the rubber blanket cylinder 12 or removed from it.

When the compressed gas flow is stopped, the cylindrical inner surface 40 of the sleeve-shaped rubber blanket 14 elastically contracts back to its original size and engages on the cylindrical outer surface 42 of the rubber blanket cylinder 12. The sleeve-shaped blanket 14 is then in firm frictional contact with the blanket cylinder 12 and will not move relative to the blanket cylinder 12 during operation of the printing unit 10.

As shown in Fig. 3, the sleeve-shaped rubber blanket 14 consists of a plurality of layers, namely it comprises a relatively rigid carrier layer 60 and a number of flexible layers supported by the carrier layer 60. The flexible layers are first and second compressible layers 62 and 64, an inextensible layer 66 and a pressure layer 68.

The carrier layer 60 is formed by a cylindrical sleeve 70, on which the cylindrical inner surface 40 is located. The cylindrical sleeve 70 is elastically slightly extensible circumferentially to facilitate the telescopic movement of the sleeve-shaped rubber blanket 14 over the rubber blanket cylinder 12, as described above. The cylindrical sleeve 70 is preferably made of metal, such as nickel, and has a thickness of approximately 13 mm, which has been found to have the required rigidity, strength and elastic properties. Alternatively, the cylindrical sleeve 70 made of polymers such as glass fiber or plastic, for example Mylar (trademark), with a thickness of approximately 76 mm.

Two primer coatings (71 and 72) help bind the first compressible layer 62 to the support layer 60. If the backing layer 60 is a nickel cylinder, the first primer 71 is preferably Chemlok 205, and the primer 72 is preferably Chemlok 220, both available from Lord Chemical Company.

"The first compressible layer 62 comprises, as shown in Fig. 3, a seamless sleeve-shaped body 74 made of an elastic polymer. The sleeve-shaped body 74 has a multiplicity of cavities which give the sleeve-shaped body 74 compressibility. In the preferred embodiment of FIG In the invention shown in the drawings, the cavities are micropores formed by a plurality of compressible microspheres 76 embedded in the sleeve-shaped body 74. Alternatively, to create compressibility in the elastic body, the cavities in the sleeve-shaped body 74 could be made of embedded particles of a compressible material other than The microspheres 76 are formed or are produced by swelling, leaching or by means of other known methods which form voids in an elastic body.

The first compressible layer 62 further includes a compressible thread 80 which extends spirally through the sleeve-shaped body 74 and around the carrier layer 60. The thread 80 is impregnated with the elastic polymer of the sleeve-shaped body 74 and with the microspheres 76. The second compressible Layer 64 likewise consists of a seamless, sleeve-shaped body 90 made of an elastic polymer, a number of compressible micropores 92 embedded in the sleeve-shaped body 90 and a compressible thread 94 which spirally extends through the sleeve-shaped body 90 and around the first compressible layer 62 extends.

The elastic polymer from which the seamless, sleeve-shaped bodies 74 and 90 are formed is preferably mixed with the microspheres 76 and results in a compressible rubber cement of the following composition: Parts 1. Butadiene copolymer and acrylonitrile with 50 parts of dioctyl phthalate (DOP) 480.00 2nd soft sulfurized factice (oil rubber) 40.00 3rd Acrylonitrile / butadiene copolymer 80.00 4th Medium thermal soot 360.00 5. Barium sulfate 80.00 6. Dioctyl phthalate 40.00 7. Benzthiazole disulfide accelerator 8.00 8th. Tetramethyl thiuram disulfide accelerator 4.00 9. Sulfur with magnesium carbonate 4.00 10th Zinc oxide activator 20.00 11. Butyl Eight 2% / weight of the total of cells 1 through 10. 12th Microspheres 6% / weight of the sum of rows 1 through 11. 13. Toluene 2.5 times the weight of the sum of rows 1 through 12.

The microspheres 76 and 92 are preferably the Expancel microspheres known under the trademark Expancel 461 DE from Sundsvall, Sweden. These microspheres have a shell, mainly consisting of a copolymer of vinylidene chloride and acrylonitrile, and contain gaseous isobutane. Other microspheres that have the desired compressibility properties can also be used, e.g. those disclosed in U.S. Patent No. 4,770,928.

The compressible threads 80 and 94 are preferably cotton threads approximately 0.13 to 0.76 mm (0.005-0.030 inch) in diameter, most preferably approximately 0.38 mm (0.015 inch) in diameter. The individual thread winding, ie the circumferentially adjacent thread sections, are preferably axially spaced approximately 0.25 mm apart. This close spacing ensures that there is practically none There are gaps between the windings. Alternatively, threads 80 and 94 can each be made of a different compressible material or can be replaced with compressible tubes.

The non-stretchable layer 66 comprises a seamless sleeve-shaped body 100 made of an elastic polymer and a longitudinally inextensible thread 102 located within the sleeve-shaped body 100. The thread 102 extends spirally through the sleeve-shaped body 100 and around the second compressible layer 64 The thread 102 is preferably cotton approximately 0.18 mm in diameter and the adjacent thread windings are spaced approximately 0.025 mm (0.001 inch) apart. Thus, the thread 102 extends in a narrow spiral, in which the adjacent windings extend essentially perpendicular to the longitudinal axis of the sleeve-shaped rubber blanket 14.

The thread 102 has a longitudinal modulus of no less than 45,359 kg per 6.452 cm ² (100,000 lbs per square inch), and in the preferred embodiment has a modulus of elasticity of approximately 381,016 kg per 6.452 cm ² (840,000 lbs per square inch). The elastic polymer of the seamless, tubular body 100 has a modulus of elasticity of approximately 245 kg per 6.452 cm ² (540 lbs per square inch). Thus, the thread 102 has a modulus of elasticity of not less than about 185 times the modulus of elasticity of the elastic polymer from which the seamless, sleeve-shaped body 100 is formed, and preferably a modulus of elasticity of about 1,555 times the modulus of elasticity of the elastic polymer. The thread spiral 102 thus forms a circumferentially inextensible, sleeve-shaped lower layer, which prevents the sleeve-shaped body 100 from stretching circumferentially. Like the threads 80 and 94, the thread 102 is included impregnated with the elastic polymer of the sleeve-shaped body 100.

Alternatively, the inextensible layer 66 could be formed from a seamless, sleeve-shaped body made of a rubber or urethane copolymer with a modulus of elasticity in the range of 454-2722 kg per 6.452 cm ² (1,000-6,000 lbs per square inch) and no underlayer the thread 102 included. These materials are available under the trademark "Airthane" from Air Products and Chemicals, Inc.

The pressure layer 68 is a seamless and gap-free sleeve-shaped body with a smooth and gap-free cylindrical outer pressure surface 110. It is formed from a relatively soft, elastic polymer, such as rubber, which is a little compliant and which adheres to the sleeve-shaped rubber blanket 14 the gap 112 between the blanket cylinder 12 and the plate cylinder 20 (Fig. 1 and 4) can exert pressure. Since the print layer 68 is elastic and resilient, it is helpful to maintain a uniform pressure on the nip 112 in order to ensure a uniform transfer of the inked print image. The print layer 68 preferably consists of the following composition: Parts 1. Polysulfide polymer 20.00 2nd Acrylonitrile / butadiene copolymer 120.00 3rd Vulcanized vegetable oil 10.00 4th Medium thermal soot 90.00 5. Barium sulfate 20.00 6. Polyester glutarate 10.00 7. Special vulcanizing agent in nitrile polymer 15.90 8th. Benzthiazole disulfide accelerator 2.00 9. Tetramethyl thiuramide sulfide accelerator 1.00 10th 75% ethylene thiourea 25% EPR (ethylene propylene rubber) binder accelerator 0.20

During operation of the printing press 10, the cylindrical outer printing surface 110 of the sleeve-shaped rubber blanket 14 moves through the nip 112 between the plate cylinder 20 and the rubber blanket cylinder 12, as shown in FIG. 4. The flexible layers 62-68 of the tubular rubber blanket 14 are pressed in at the nip 112 by the rigid surface of the pressure plate 18. The pressure layer 68 is not compressible, so it retains its original thickness as it moves through the nip 112. The non-stretchable layer 66 is easily compressible due to the compressibility of the thread 102, so it is slightly compressed during the movement through the nip 112. It is important that the thread 102 is non-stretchable in the longitudinal direction and that the non-stretchable layer 66 will resist radial bulging as it is moved through the nip 12. The non-stretchable layer 66 prevents the portion of the printing layer located in the printing nip from stretching more than 0.025 mm (0.001 inch) in the circumferential direction, and in fact, in the preferred embodiment, the portion of the printing layer in the printing nip stretches significantly less than 0.025 mm ( 0.001 inch). The non-stretchable layer 66 also largely prevents the formation of standing waves in the printing layer 68 on both sides of the nip (see prior art FIG. 5). Such standing waves lead to smearing of the printing ink.

The first and second compressible layers 62 and 64 are both compressed at the nip 112. It is known that compressible parts of a rubber blanket become hot due to the continuous compression and regression in use. In the compressible layers 62 and 64, the cotton material has the compressible Threads 80 and 94 have less of a tendency to heat than the elastic polymer of sleeve-shaped bodies 74 and 90. Thus, the sleeve-shaped rubber blanket 14 according to the invention has little tendency to become overheated in use, since the compressible layers 62 and 64 are at least partially made of one material that stays cooler than the elastic polymer.

The pressure layer 68 and the elastic bodies 74, 90 and 100 of the layers 62, 64, 66 under the pressure layer 68 are endless bodies without gaps or seams. Furthermore, the spirally wound threads 80, 94 and 102 do not form any seams or gaps extending axially along the sleeve-shaped rubber blanket 14. Therefore, the cross-sectional shape of the tubular rubber blanket 14 moving through the nip 112 remains unchanged with each complete rotation of the rubber blanket cylinder 12. The pressure ratio between the outer pressure surface 110 and the pressure plate 18 also remains unchanged during the movement through the nip 112. The shocks and vibrations that occur in known rubber blankets with an axially extending gap are thus avoided, and a smooth transfer of the printed image is ensured.

The present invention further contemplates possible manufacturing processes for a tubular rubber blanket. In a preferred method of manufacturing the tubular rubber blanket 14 as shown in FIG. 3, the chemlok 205 primer coating 71 is applied to the cleaned surface of the backing layer 60 and cured for about 30 minutes. Then the second primer coating 72 made of Chemlok 220 is applied and cured for about 30 minutes. Thereafter, the first compressible layer 62 is applied over the precoated backing layer 60 by embedding the thread 80 in the compressible rubber cement and the embedded thread 80 is wound spirally around the pre-coated carrier layer 60. As shown schematically in FIG. 6, the thread 80 is embedded in the rubber putty by pulling it during winding from a spool 22 around the carrier layer 60 through the rubber putty in a container 120. An additional dose of rubber cement is then applied over the wound thread 80 as needed to form an additional thickness of the first compressible layer 62 in the area 126 shown in FIG. 3. The first compressible layer 62 is then cured for two hours and oven dried for four hours at 60 ° C (140 ° F). The second compressible layer 64 is formed in the same manner. If desired, additional windings of compressible thread may be applied to either or both of the compressible layers 62 and 64.

As mentioned above, compressible materials other than the microspheres 76 and 92 could be used to form the cavities that impart compressibility to the sleeve-shaped bodies 74 and 90 in the compressible layers 62 and 64. Alternatively, the cavities could be created by means of known methods by swelling and / or leaching after the sleeve-shaped bodies 74 and 90 have been built up over the carrier layer 60.

The inextensible layer 66 shown in FIG. 3 is formed in a similar manner by embedding the thread 102 in an elastic polymer without microspheres and winding it spirally around the second compressible layers 62 and 64. The embedded thread 102 is preferably completely impregnated with the elastic polymer and wound under tension in order to apply a radially compressive preload to the compressible layers 62 and 64. Then the inextensible layer 66 is air dried for 15 minutes.

Next, a layer of unvulcanized printing rubber, 1 mm (0.040 inch) thick, is wrapped over the non-compressible layer 66 to form the printing layer 68. This construction is wrapped with 5.72 cm (2.25 inches) nylon tape (not shown) and in a drying oven for four hours at approximately 100 ° C (200 ° F) and for four hours at approximately 150 ° C (292 ° F) cured. The contiguous edges of the wrapped rubber layer are split, but combine during curing, so that the finished printing layer 68 has no axially extending seam. The overlying bodies 74, 90 and 100 made of elastic polymer also bond during curing. Layers 62-68 can then be identified by their various components as shown in Figure 4, but they are not separate from one another. Accordingly, the elastic polymers of layers 62-68 form a single, endless and seamless sleeve-shaped body made of elastic polymer after curing. Because the inextensible layer 66 is also compressible, layers 62-66 effectively form a composite compressible layer having a lower portion containing compressible thread and microspheres and an upper portion containing compressible thread without microspheres. After curing, the nylon tape is removed and the print layer 68 is sanded to a thickness of about 0.3 mm to 0.5 mm (0.013-0.020 inch) and processed to create a smooth, endless outer print surface 110.

7 shows an alternative embodiment of a compressible layer for the tubular rubber blanket according to the invention. The compressible layer 150 in FIG. 7 consists of a seamless, sleeve-shaped body 152 made of elastic polymer, microspheres 154 and ground cotton fibers 156. The microspheres 154 and the ground cotton fibers 156 are evenly distributed in the sleeve-shaped body 152 in order to compress the layer 150 to lend.

As with any other embodiment of the invention, the voids formed by microspheres 154 and / or fibers 156 could be created by the alternative methods described above. How about the If threads 80 and 94 are in the compressible layer 62 and 64 described above, the ground cotton fibers 156 have a relatively low tendency to become overheated by the repeated compression at the nip between a blanket cylinder and a plate cylinder.

8A and 8B schematically illustrate methods of applying a compressible layer 150 of a measured thickness over the precoated carrier layer 60 by metering a rubber cement mixture with a metering roller 158 and a doctor blade 160. 8C schematically illustrates a method in which the compressible layer 150 is applied by spraying a rubber cement mixture in a measured thickness over the precoated carrier layer 60. The pressure layer 68 could alternatively be formed by a metering process or by spraying the elastic polymer, and / or the compressible layers 62, 64 and 150 could alternatively be formed by wrapping calendered layers, with the open edges not forming an axial seam after curing .

9A and 9B illustrate another alternative embodiment of a compressible layer for the sleeve-shaped rubber blanket according to the invention. As shown in FIG. 9A, a compressible layer 170 is shaped as a seamless cylindrical casting. The compressible layer 170 is made of the same material as the compressible layer 150 described above and has an inner diameter which is not greater than the outer diameter of the support layer 60. When the compressible layer 170 is radially stretched, as shown in Fig. 9B, it can these are pushed telescopically over the carrier layer 60. Then the compressible layer 170 can contract and is thus installed in a state of radial and circumferential tension.

10 is a schematic representation of an alternative embodiment of a circumferentially inextensible lower layer of the sleeve-shaped rubber blanket according to the invention. As shown in FIG. 10, the thread 102 is inextensible in the longitudinal direction woven to form a sleeve 200 that can be telescopically slid over the compressible layers 62 and 64 as shown in FIG. 3. The pattern of woven thread 102 does not allow axial or radial expansion of the sleeve 200. In a preferred method of making a sleeve-shaped rubber blanket with the sleeve 200, elastic polymer is applied to a shallow depth over a second compressible layer 64 and the sleeve 200 then becomes telescopic slid over the elastic polymer and the second compressible layer 64. Additional elastic polymer is applied to the sleeve 200 as needed to embed and saturate the thread 102 therein and to achieve the desired thickness of the complete inextensible layer. In this embodiment of the invention, the thread 102 can be shrunk by the application of heat. The shrunk sleeve 200 would be in circumferential and axial tension and would apply a compressive preload to the compressible layers 62 and 64 below.

11A and 11B are schematic representations of a further alternative embodiment of a circumferentially inextensible lower layer of the sleeve-shaped rubber blanket according to the invention. As shown in FIG. 11A, the longitudinally inextensible thread 102 is knitted into a sleeve 210 which can be telescopically pushed over the compressible layers 62 and 64, as shown in FIG. 3. The pattern of the knitted thread 102 allows the sleeve 210 to be axially extended, the diameter of which is reduced, as indicated in FIG. 11B. In a preferred method of making a sleeve-shaped rubber blanket with sleeve 210, an elastic polymer is applied at a shallow depth over the second compressible layer 64 and the sleeve 210 is telescopically pushed over the elastic polymer and the compressible layer 64. The sleeve 210 is then axially extended and their Diameter decreases. The elongated sleeve 210 is in circumferential and axial tension and acts on the compressible layers 62 and 64 underneath with a radially compressive preload. Additional elastic polymer is applied to the elongated sleeve 210 to impregnate the thread 102 and achieve the desired thickness of the complete, inextensible layer. When cured, the elastic polymer forms a seamless, sleeve-shaped body in which the elongated sleeve 210 is embedded.

12 is a sectional view of a further alternative embodiment of a circumferentially non-stretchable lower layer of the sleeve-shaped rubber blanket according to the invention. As shown in FIG. 12, an endless piece of plastic film 230 spirally extends through the elastic polymer 232 of an inextensible layer and around a compressible layer 234. The film 230 is preferably of a width approximately equal to the length of the tubular rubber blanket and one Thickness of only 0.03 mm (0.001 inch) so that the narrow seam of the top layer formed by the 0.03 mm wide edge 236 does not break through the smooth, endless outer contour of an overlying printing layer.

13 is part of a sectional view of another alternative embodiment of the invention. As shown in Fig. 13, a sleeve-shaped blanket 250 is comprised of a relatively rigid backing, a pair of seamless sleeve-shaped, microspherical rubber kit layers 254 and 256, and a pair of sleeve-shaped, compressible fabric layers 258 and 260. The compressible fabric layers 258 and 260 are preferably woven or knitted sleeves as shown in Figs. 10, 11A and 11B. The upper compressible fabric layer 260 is best described as one circumferentially inextensible sleeve attached so that it forms an inextensible layer of the sleeve-shaped rubber blanket 250. With the help of an intermediate layer 262 made of ordinary rubber cement, a sleeve-shaped pressure layer 264 is connected to the upper compressible fabric layer 260.

From the foregoing description of the invention, those skilled in the art will understand the improvements, changes and modifications for which patent protection is sought within the scope of the invention in the appended claims.

Claims (42)

1. Tubular blanket (14) for a blanket cylinder (12) in an offset printing machine (10), which has:

   - a cylindrical sleeve (70) which can be moved axially over a blanket cylinder (12);

   - a compressible layer (62) over the sleeve (70), the compressible layer (62) having a first, seamless, tubular body (74) made of elastic material having a multiplicity of cavities (76, 92, 154); and

   - a non-extensible layer (66) over the compressible layer (62), the non-extensible layer (66) having a second, seamless, tubular body (100) made of elastic material and a tubular sublayer (102) made of a material, which is non-extensible in the circumferential direction, for the compressive pretensioning of the layers (62, 64) acting in the radial direction.
2. Blanket according to Claim 1, characterized in that, in the said first, seamless, tubular body (74) made of elastic material, the said cavities comprise a multiplicity of micropores which are distributed uniformly in the said first, seamless, tubular body (74) made of elastic material.
3. Blanket according to Claim 2, characterized in that the said micropores are formed by microspheres (76, 92, 154) which are distributed evenly in the said first, seamless, tubular body (74) made of elastic material.
4. Blanket according to Claim 1, characterized in that the said cavities in the said first, seamless, tubular body (74) made of elastic material are formed by pieces of compressible threads which are arranged in the said first, seamless, tubular body (74) made of elastic material.
5. Blanket according to Claim 1, characterized in that the said sleeve (70) is elastically extensible in the radial direction for the purpose of mounting the said blanket (14) over a blanket cylinder (12).
6. Blanket according to Claim 1, characterized in that the said cavities in the said compressible layer (62) comprise a multiplicity of micropores which are defined by a multiplicity of microspheres (76, 92, 154) arranged in the said first, seamless, tubular body (74) made of elastic material,

   - the said compressible layer (62) furthermore comprising a compressible fibre material (80) in the said first, seamless, tubular body (74) made of elastic material,

   - the said compressible fibre material (80) being impregnated with the said elastic material and with the said microspheres (76, 92, 154).
7. Blanket according to Claim 6, characterized in that the said compressible fibre material (80) comprises cotton fibres which are distributed in the said first body (74) made of elastic material.
8. Blanket according to Claim 6, characterized in that the said compressible fibre material (80) consists of a thread which extends helically around the said sleeve (70).
9. Blanket according to Claim 1, characterized in that the said compressible layer (62) exerts a compressive pretension acting in the radial direction on the said sleeve (70).
10. Blanket according to Claim 1, characterized in that the said tubular sublayer (102) made of a material (102) which is non-extensible in the circumferential direction comprises a thread (102) which in non-extensible in the longitudinal direction and which extends helically through the said second, seamless, tubular body (100) made of elastic material and around the said compressible layer (62).
11. Blanket according to Claim 10, characterized in that adjacent sections of the said thread (102) running in the circumferential direction extend in directions which are disposed essentially perpendicular to the axis of the said sleeve (70).
12. Blanket according to Claim 11, characterized in that the said thread (102) exerts a compressive pretension acting in the radial direction on the said compressible layer (62).
13. Blanket according to Claim 12, characterized in that the said thread (102) is impregnated with the elastic material of the said tubular body (100).
14. Blanket according to Claim 1, characterized in that the non-extensible layer (66) exerts a compressive pretension in the radial direction on the said compressible layer (62) and has a modulus of elasticity of at least 6.9 × 10⁸ Pa (100,000 lbs per square inch).
15. Blanket according to Claim 14, characterized in that the said tubular sublayer (102) of material which is non-extensible in the circumferential direction comprises a seamless sleeve (200) of woven threads (102) which is pretensioned in the circumferential direction and in the axial direction.
16. Blanket according to Claim 14, characterized in that the said tubular sublayer (102) made of a material which is non-extensible in the circumferential direction comprises a seamless sleeve (210) of knitted threads (102), which is pretensioned in the circumferential direction and in the axial direction.
17. Blanket according to Claim 1, characterized in that the said tubular sublayer (102) made of a material which is non-extensible in the circumferential direction comprises layers of plastic film (230) located one above another.
18. Blanket according to Claim 17, characterized in that the said layers of plastic film (230) located one above another are adjoining sections of a continuous piece of plastic film (230) which is wound helically around the said compressible layer (62).
19. Blanket according to Claim 18, characterized in that the said plastic film (230) has a thickness of about 0.025 mm.
20. Tubular blanket (14) according to Claim 1, having

    - a cylindrical sleeve (70) which can be moved in the axial direction over a blanket cylinder (12);

    - a compressible layer (62) over the sleeve (70), the compressible layer (62) having a first, seamless, tubular body (74) made of elastic material having a multiplicity of cavities (76, 92, 154); and

    - a non-extensible layer (66) over the compressible layer (62), the non-extensible layer (66) having a second, seamless, tubular body (100) made of elastic material; and

    - a seamless, tubular impression layer (68) over the non-extensible layer (66), the impression layer (68) having a continuous, gapless, cylindrical printing surface (110).
21. Blanket according to Claim 20, characterized in that the said second, seamless, tubular body (100) made of elastic material has a modulus of elasticity of 6.9 × 10⁶ to 4.1 × 10⁷ Pa (1000 to 6000 lbs per square inch).
22. A method for the manufacture of a tubular blanket (14) for a blanket cylinder (12) in an offset printing machine (10), which comprises the following steps:

    - forming a first layer (62) of the said tubular blanket (14) by applying a first batch of an elastic material in a seamless, cellular, tubular form onto a cylindrical sleeve (70); and

    - forming a second layer (66) of the said tubular blanket (14) by applying a second batch of an elastic material in a seamless, tubular form onto the said first layer (62); and

    - embedding a material which is non-extensible in the circumferential direction in the said second batch of the elastic material.
23. Method according to Claim 22, which furthermore comprises the following steps:

    - forming an impression layer (68) of the said tubular blanket (14) by applying a third batch of an elastic material in a seamless, tubular form onto the said second layer (66) and

    - forming a continuous, cylindrical printing surface on the said impression layer (68).
24. Method according to Claim 22, characterized in that the said first layer (62) of the said tubular blanket (14) is formed by

    - embedding compressible microspheres (76, 92, 154) in the said first batch of elastic material in order to form a compressible, composed, cellular material and

    - applying the said compressible, composed, cellular material in a seamless, tubular form onto the said sleeve (70).
25. Method according to Claim 24, characterized in that the said compressible, composed, cellular material is formed by embedding a compressible fabric (80) and the said microspheres (76, 92, 154) in the said first batch of the elastic material.
26. Method according to Claim 24, characterized in that the said compressible, composed, cellular material is formed by coating a thread of a compressible fabric with a mixture of the said first batch of elastic material and microspheres (76, 92, 154) and is applied by winding the said coated thread in a helical manner around the said sleeve (70) in a seamless, tubular form.
27. Method according to Claim 24, characterized in that the said compressible, composed, cellular material is formed by dispersing compressible fabric fibres (156) in the said first batch of elastic material and is applied by application of a predetermined thickness around the said sleeve (70).
28. Method according to Claim 27, characterized in that the said compressible, composed, cellular material is applied in the predetermined thickness around the said sleeve (70) by means of a doctor (160).
29. Method according to Claim 27, characterized in that the said compressible, composed, cellular material is applied in the predetermined thickness to the said sleeve (70) by means of a metering roller (158).
30. Method according to Claim 24, characterized in that

    - the said compressible, composed, cellular material is formed as a seamless, cylindrical casting (170) with an internal diameter which is not greater than the external diameter of the said sleeve (70); and

    - the said casting (170) is applied to the said sleeve (70) by radial stretching and pushing-on in the axial direction.
31. Method according to Claim 22, characterized in that the said second layer is formed by

    - coating a thread (102), which is non-extensible in the longitudinal direction, with the said second batch of the elastic material; and

    - winding the said coated thread (102) in a helical fashion around the said first layer (62).
32. Method according to Claim 31, characterized in that sections of the said thread (102) located adjacently in the circumferential direction are wound in such a way that they extend essentially perpendicular to the said sleeve (70).
33. Method according to Claim 22, characterized in that the said second layer (66) is formed by

    - telescopically moving a knitted sleeve (210) of a thread (102), which is non-extensible in the longitudinal direction, over the said first layer (102); and

    - axially extending the said knitted sleeve (210) in order to reduce its diameter and to exert a compressive pretension in the radial direction on the said first layer (62).
34. Method according to Claim 22, characterized in that the said second layer (66) is formed by

    - telescopically moving a woven sleeve (200) of a thread (102), which is non-extensible in the longitudinal direction, over the said first layer (62); and

    - shrinking the said thread (102) in order to reduce the diameter of the said woven sleeve (200) and to exert a compressive pretension in the radial direction on the said first layer (62).
35. Tubular blanket (14) according to Claim 1, having

    - an elastic, tubular carrier layer (60) which can be moved axially over the blanket cylinder (12);

    - a compressible layer (62) which is arranged above the elastic, tubular carrier layer (60) and contains a compressible thread (80), rubber mastic (74) and microspheres (76);

    - a tubular body (100, 102) which is mounted over the carrier layer (60) and the compressible layer (62) and has a seamless, tubular body (100) made of elastic material and a tubular sublayer (102) made of a material which is non-extensible in the circumferential direction and

    - an outer seamless and gapless impression layer (68).
36. Tubular blanket (14) for an offset printing machine (10) according to Claim 35, which comprises:

    - an elastic, tubular carrier layer (60) which can be moved axially over the blanket cylinder (12);

    - a compressible layer (62, 64) which consists of at least one radial layer on the said carrier layer (60) of a compressible thread (80) which is embedded in a rubber mastic (74) containing microspheres (76), the said radial layer of thread (80), rubber mastic (74) and microspheres (76) forming a continuous layer (62);

    - a non-extensible layer (66) which comprises at least one adjoining radial layer of a non-extensible thread (102) with rubber mastic (100) without microspheres (76), applied to the first layer located below it; and

    - an outer impression layer (68) which forms a continuous, gapless outer surface.
37. Tubular blanket (14) according to Claim 36, characterized in that the compressible layer (62-64) consists of at least two radial layers of compressible thread (80, 94) in a rubber mastic (74, 90) containing microspheres (76, 92).
38. Tubular blanket (14) according to Claim 36, characterized in that the compressible thread (80, 94) consists of cotton.
39. Tubular blanket (14) according to Claim 36, characterized in that the elastic, tubular carrier layer (60) is a nickel cylinder (70).
40. Tubular blanket (14) according to Claim 1, characterized in that the compressible layer consists of a pair of seamless, tubular rubber-mastic layers (254, 256) containing microspheres.
41. Tubular blanket (14) according to Claim 1, characterized in that the non-extensible layer consists of a pair of tubular,, compressible fabric layers (258, 260).
42. Tubular blanket (14) according to Claim 41, characterized in that the tubular, compressible base layer (260) located nearest to a tubular impression layer (264) is non-extensible in the circumferential direction.

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